Venezuelan security forces and demonstrators faced off in streets blocked by burning barricades in several provincial cities on Thursday as protests escalated against President Nicolas Maduro's socialist government.

At least five people have died since the violence broke out last week, the most serious unrest since Maduro was narrowly elected in April 2013. There have been scores of injuries and arrests.

The protesters, mostly students, want Maduro to resign, and blame his government for violent crime, high inflation, product shortages and alleged repression of opponents.

Thursday's most serious unrest was in the western Andean states of Tachira and Merida, which have been especially volatile since hardline opposition leaders called supporters onto the streets in early February demanding Maduro's departure.

In the city of San Cristobal, which some residents are describing as a "war zone", many businesses remained shut as students and police faced off again. The government says it is taking "special measures" to restore order in Tachira.

"This is not a militarisation," Interior Minister Miguel Rodriguez Torres said on state TV from San Cristobal.

"We are here to work for the great majority of people in Tachira. ... Before we have dialogue, we must have order."

Maduro says he will not let his rivals turn Tachira into "a Benghazi," referring to the violence-wracked Libyan city.

Wednesday night saw one of the worst bouts of violence the capital Caracas has seen during nearly three weeks of unrest.

Around a square in the wealthier east of the city, security forces fired teargas and bullets, chasing youths who hurled Molotov cocktails and blocked roads with burning piles of trash.

"I declare myself in civil disobedience," read one banner held up by demonstrators on a city road early on Thursday.

"DON'T GIVE UP!"

Caracas was much calmer during the day, though a few hundred opposition demonstrators gathered again at dusk in the same square, Plaza Altamira. Some businesses stayed closed, in a further drag on the already ailing economy.

The government said a funeral parade for deceased folk singer Simon Diaz, a beloved figure who died on Wednesday aged 85, was held up due to "violent groups" blocking roads.

Tensions have escalated since opposition leader Leopoldo Lopez, a 42-year-old Harvard-educated economist, turned himself in to troops this week. He is being held in Caracas' Ramo Verde military jail on charges of fomenting the violence.

"Change depends on every one of us. Don't give up!" Lopez's wife, Lilian Tintori, said on Twitter.

Local TV channels are providing almost no live coverage of the unrest, so Venezuelans are turning to social media to swap information and images, though falsified photos are circulating.

Both sides rolled out competing evidence of the latest violence on Thursday, with ruling Socialist Party governors showing photos and video of charred streets and torched vehicles, while the opposition posted footage of brutal behavior which they said was by national guard troops.

Maduro, elected last year to succeed socialist leader Hugo Chavez, says Lopez and "small fascist groups" are in league with the U.S. government and want a coup.

He has been sharply critical of international media coverage, and on Thursday he warned CNN Espa�ol it risked being kicked out of the country if it didn't "rectify" its ways.

Speaking in Mexico, US President Barack Obama criticized Maduro's government for arresting protesters and urged it to focus on addressing the "legitimate grievances" of its people.

"GROSS INTERFERENCE"

That brought a typically scathing response from Caracas.

Obama's comments were "a new and gross interference" in its internal affairs, Venezuela's government said in a statement.

"Independent governments and the people of the world want the US government to explain why it funds, encourages and defends opposition leaders who promote violence in our country."

Street protests were the backdrop to a short-lived coup against Chavez in 2002 before military loyalists and supporters helped bring him back. There is no evidence the military, which was the decisive factor in 2002, may turn on Maduro now.

Countries around the region are watching closely. Political allies such as Cuba, which receives Venezuelan oil on preferable terms, have denounced an opposition "coup attempt", while other nations have called for dialogue between the two sides.

Detractors call Lopez a dangerous hothead. He has frequently squabbled with fellow opposition leaders and was involved in the 2002 coup, even helping arrest a minister.

Though the majority of demonstrators have been peaceful, an increasingly prominent radical fringe has been attacking police, blocking roads and vandalising buildings.

Though the Caracas protests began and are still strongest in middle-class neighborhoods, sporadic demonstrations have also spread to poorer areas of the city, residents say.

Rights groups say the police response has been excessive, and some detainees say they were tortured.

Venezuela's main opposition leader, Henrique Capriles, who narrowly lost to Maduro in last year's presidential election, disagrees with Lopez's street tactics but backs protesters' grievances and has condemned the government response.

"How many more deaths do they want?" he said to reporters on Thursday, urging opposition activists to avoid violence.